A number of devices, for example as disclosed in U.S. Pat. No. 3,343,484, entitled LITHOGRAPHIC DAMPENER WITH SKEWED METERING ROLLER; U.S. Pat. No. 3,647,525, entitled METHOD AND MEANS FOR APPLYING LIQUID TO A MOVING WEB; U.S. Pat. No. 3,937,141, entitled DAMPENER FOR LITHOGRAPHIC PRINTING PLATES; U.S. Pat. No. 3,986,452, entitled LIQUID APPLICATOR FOR LITHOGRAPHIC SYSTEMS; and U.S. Pat. No. 4,041,864, entitled METHOD AND APPARATUS FOR INKING PRINTING PLATES, employ rollers urged into pressure indented relation and driven at different surface speeds to form a film of liquid of controlled thickness on the surface of one of the rollers.
Heretofore, it has been standard procedure for pressmen operating dampeners of the type disclosed in U.S. Pat. No. 3,343,484, to establish pressure between a metering roller and a transfer roller to form a film of the required thickness for application over one or more form rollers to the surface of a lithographic printing plate. The metering roller and transfer roller in such systems are often mounted in a common frame as disclosed in U.S. Pat. No. 3,168,037 to assure that the pressure between adjacent surfaces of the metering roller and the transfer roller will not be disturbed when the transfer roller is moved into and out of engagement with the surface of a form roller.
Generally, at least one of the metering and transfer rollers has been supplied with a resilient surface which is intended by the surface of the other roller and surfaces of the metering and transfer rollers are often driven at different surface speeds to accomplish metering of films of the desired thickness. When operating, dampening fluid is spread over the surfaces of the metering and transfer rollers and the liquid functions as a lubricant to maintain hydraulic separation between the surfaces which are moving at different surface speeds. However, when such systems are being made ready for operation, surfaces of the metering roller and transfer roller are generally dry and the lubricating layer of dampening fluid is not present. The dry surfaces of the rollers tend to stick together due to increased friction coefficient, resulting in damage to the surface of the resilient covered roller. Slippage between the driven dry surfaces also, scuffs or otherwise damages the resilient roller surface. In addition, in some instances, damage to the mechanical and elctrical drive systems has resulted when attempting to slip dry, heavily indented, surfaces of the rollers against each other.